Grocery clerks in San Francisco no longer have to ask that old question that's become nearly synonymous with grocery shopping: "Paper or plastic?" Now San Francisco residents will only have the option of paper, because the city became the first in the U.S. to ban plastic shopping bags. Other cities are weighing similar options and may follow suit.

Plastic bags are of environmental and political concern to those who acknowledge the role that plastic bags require use of the limited supply of petroleum, and because the bags do not decompose easily. However, unlike the choice of walking or driving a car, this issue does not have a clear winner in terms of environmental impact. The Environmental Protection Agency states that plastic bags require 40 percent less energy to produce and generate 80 percent less solid waste than paper bags. However, plastic bags also have a long list of disadvantages as well. Although plastic bags can be reused, fewer than one percent actually are. Plastic bags are also made from a non-renewable resource that is already in limited supply, and they take more than a thousand years to decompose. That's a lot of discarded grocery bags sitting in landfills.

The downside to banning plastic bags is that paper bags are more expensive for retailers who are often already operating on very slim profit margins. Plastic bags cost about a penny each, the new compostable bags are as high as 10 cents each, and paper is a nickel,'' said Kroger spokesman Dale Hollingsworth in The Ann Arbor News. "The difference between a penny and a nickel when you are operating on a 1 to 2 percent net profit can be the difference between being (in the) black or red.''

Retailers are considering other alternatives aimed at reducing use of plastic bags. Beginning in June, Michigan-based Meijer, Inc. will offer shoppers the option to buy 99-cent reusable nonwoven plastic bags made of recyclable polypropylene. Whole Foods Market has also considered biodegradable shopping bags, but ultimately rejected the option because they are made of genetically modified corn. Whole Foods continues to look for other alternatives, and in the meantime, offers shoppers 10 cents for every paper bag used on subsequent trips.